Non-linear Navigation of a Three Dimensional Stereoscopic Display

ABSTRACT

Systems and methods for navigating a 3D stereoscopic scene displayed via a 3D stereoscopic display system using user head tracking. A reference POV including a reference user head position and a reference user head orientation may be established. The user head POV may be tracked, including monitoring user head positional displacements and user head angular rotations relative to the reference POV. In response to the tracking, a camera POV used to render the 3D stereoscopic scene may be adjusted based on a non-linear mapping between changes in the camera POV and the user head positional displacements and user head angular rotations relative to the reference POV. The non-linear mapping may include a mapping of user head positional displacements relative to the reference POV to translational movements in the camera POV and a mapping of user head angular rotations relative to the reference POV to rotations in the camera POV.

PRIORITY DATA

This application claims benefit of priority to U.S. ProvisionalApplication Ser. No. 61/814,319, titled “Non Linear Navigation”, filedApr. 21, 2013, whose inventors are Scott M. Dolim and CiscoLopez-Fresquet, which is hereby incorporated by reference in itsentirety as though fully and completely set forth herein.

TECHNICAL FIELD

This disclosure relates to the field of digital display, and moreparticularly to non-linear navigation of a 3D scene via user headmovements.

DESCRIPTION OF THE RELATED ART

Three dimensional (3D) displays (actually, simulated 3D, e.g., viastereo display (SD) techniques) are increasingly utilized for a varietyof applications, including, for example, remote viewing,videoconferencing, video collaboration, and so forth.

FIG. 1 illustrates a modern display chain, according to typical priorart embodiments, which includes the following components:

1. GPU—Graphics Processing Unit. This component resides on a personalcomputer, workstation, or functional equivalent, and outputs videolevels for each color or channel of a supported color model, e.g., foreach of three colors, typically Red (R), Green (G), and Blue (B), foreach pixel on the display. Each of these numbers is typically an 8 bitnumber, with a range of 0 to 255, although other ranges are possible.

2. Scaler—This component takes as input the video levels (e.g., for R,G, and B) for each pixel output from the GPU, and processes them invarious ways, before outputting (usually) modified video levels for RGB,usually in the same 8-bit range of 0-255.

3. Panel—This component is the display itself, typically a liquidcrystal display (LCD), but other displays are possible, and takes asinput the video levels (e.g., for R, G and B) for each pixel as outputfrom the scaler, and converts them to voltages, which are then deliveredto each pixel on the display. The panel itself may modify the videolevels before converting them to voltages.

The video chain generally modifies the video levels in two ways thathave associated shortcomings for stereo displays, specifically, gammacorrection, and overdrive. Note that the functionality described aboveis typically implemented in the scaler, but is sometimes implemented atleast partially in other devices or elements of the video chain, e.g.,in the GPU or display device (panel).

Time Sequential Stereo Displays

Unlike a normal display, in a stereo display, for each video frame thereare two images—right and left. The right image must be delivered to onlythe right eye, and the left image must be delivered to only the lefteye. In a time sequential stereo display, this separation of right andleft images is performed in time, i.e., the left and right images arepresented sequentially, and thus, contains some time-dependent elementwhich separates these two images. There are two common architectures.

The first architecture uses a device called a polarization switch (PS)which may be a distinct (separate) or integrated LC device or othertechnology switch, which is placed in front of the LCD panel (or anyother type of imaging panel, e.g., an OLED (organic light emittingdiode) panel), a plasma display, etc., or any other pixelated paneldisplay used in a time-sequential stereo imaging system, specifically,between the display panel and the viewer, as shown in FIG. 2. Thepurpose of the PS is to switch the light transmitted from the displaypanel between two orthogonal polarization states. For example, one ofthese states may be horizontally linearly polarized light (horizontallinear polarization state), and the other may be vertically linearlypolarized light (vertical linear polarization state); however, otheroptions are possible, e.g., left and right circular polarization states,etc., the key feature being that the two polarization states areorthogonal.

This allows achievement of the stereo effect shown in prior art FIG. 3.As may be seen, the top portion of the figure shows the (display) panelswitching between a left image and a right image. Synchronous with thepanel switching, the PS is switching between a Left State and a RightState, as shown. These two states emit two corresponding orthogonalpolarization states, as mentioned above. As FIG. 3 further shows, thesystem includes stereo eyewear that is designed such that the left lenswill only pass the Left State polarization and the right lens will onlypass the Right State polarization. In this way, separation of the rightand left images is achieved.

The second conventional architecture uses stereo shutter glasses, whichreplace (or integrate the functionality of) the PS and eyewear. In suchsystems, each eye is covered by an optical shutter, which can be eitheropen or closed. Each of these shutters is opened and closedsynchronously with the display panel in such a way that when the leftimage is shown on the display, only the left eye shutter is open, andwhen the right image is shown on the display, only the right eye shutteris open. In this manner, the left and right views are (alternatingly)presented to the user's left and right eyes, respectively.

Interaction with the 3D Display System

Recent advances in body tracking systems allow for new mechanisms totrack the position of a user. In particular, it has become moreprevalent to track the position of the user's head as the user interactswith a 3D scene displayed on a display screen of a stereoscopic 3Ddisplay system. Better knowledge of the position of the user's head hasled to new ways for the user to interact with the display. For example,the user's head position, and more particularly, changes in the user'shead position, may be used to effect navigation through, and renderingof, a virtual 3D scene.

In particular, the user's head position may be close to the screen orfar away from the screen. Additionally, the virtual 3D scene may haveobjects rendered at various depths within a view volume (frustum)relative to the user's point of view. Thus, for example, objects may berendered to appear in front of the display screen (negative parallax),near the display screen (near zero parallax), or behind the displayscreen (positive parallax). However, depending on the position of theobjects relative to the user's point of view, the stereo conditions maycause the imagery to be distorted or uncomfortable to the view becauseof excessive positive or negative parallax, depth of scene, andforeground (nearest to the user) artifacts resulting from near planeclipping.

Thus, improved techniques for interacting with 3D stereoscopic displaysare desired.

SUMMARY

Various embodiments of a system and method for navigating a threedimensional (3D) stereoscopic scene displayed via a 3D stereoscopicsystem are presented. The system may include a processor or functionalunit, a display screen, and a user control element. The functional unitmay be configured to perform user head tracked navigation of the 3Dscene. Further, in some embodiments, a memory medium may storeprogramming instructions executable by a processor to perform user headtracked navigation of the 3D scene.

Thus, in one embodiment a user head tracking navigation mode of a 3Dstereoscopic system may be enabled, either at startup of the 3Dstereoscopic system or through some form of user interaction that maytrigger startup of the head tracking navigation mode. The trigger may beselection of the head tracking navigation mode via a user interfacedisplayed within a 3D scene, such as a menu. Additionally, the triggermay be external to the 3D scene. Thus, the trigger may be via a usercontrol element such as a switch or button of the user control element.The user control element may be a stylus. Note that the system mayinclude more than one trigger.

Once the head tracking navigational mode has been enabled, a referencepoint of view (POV) may be established. The reference POV may include areference user head position and a reference user head orientation.Further, user head POV may be tracked. Tracking the user's head POV maymonitor user head positional displacements and user head angularrotations relative to the reference POV.

In response to tracking the user's head POV, a camera POV used to renderthe 3D stereoscopic scene may be adjusted. The adjustment may be basedon a non-linear mapping between changes in the camera POV and the userhead positional displacements and user head angular rotations relativeto the reference POV. The camera POV may correspond, or correlate to, afrustum, or frustum field of view angle, used to render the 3Dstereoscopic scene.

The non-linear mapping may include a mapping of user head positionaldisplacements relative to the reference POV to translational movementsin the camera view. Further, the non-linear mapping may include amapping of user head angular rotations relative to the reference POV torotations in the camera POV. In some embodiments, the mapping may alsoinclude a mapping of rate of change of user head positionaldisplacements relative to the reference POV to rate of change oftranslational movements in the camera POV and a mapping of rate ofchange of user head angular rotations relative to the reference POV torate of change of rotations in the camera POV.

In one particular embodiment, adjusting the camera POV may also includeadjusting one or more 3D stereoscopic rendering variables. In suchembodiments, the adjustment may also be based on a non-linear mapping ofeach of the one or more 3D stereoscopic rendering variables to thecamera POV, where the 3D stereoscopic rendering variables may include aworld scale variable, a stereo level variable, a zero parallax offsetvariable, and a head-tracking scale variable.

Note that in some embodiments, the mapping may be performed via acorrelated table of mapped variables. In other embodiments, the mappingmay be performed via a continuous function. In certain embodiments, themapping may be performed via a discontinuous function.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present disclosure can be obtained whenthe following detailed description of the preferred embodiment isconsidered in conjunction with the following drawings, in which:

FIG. 1 illustrates a modern display chain, according to the prior art;

FIG. 2 illustrates an architecture that utilizes a polarization switch,according to the prior art;

FIG. 3 illustrates a stereo effect (simulated 3D) using polarizationswitching between left and right views, according to the prior art;

FIG. 4 illustrates a 3D stereoscopic display system according toembodiments;

FIGS. 5A-5C illustrate changes to a frustum based on changes in user POVaccording to embodiments;

FIG. 6 illustrates an example of an embodiment of the non-linear mappingwith respect to frustum field of view angle as the world scale of the 3Dscene is adjusted; and

FIG. 7 illustrates an exemplary embodiment of a method for navigating athree dimensional (3D) stereoscopic scene displayed via a 3Dstereoscopic display system according to embodiments.

Although the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and are herein described in detail. It should beunderstood, however, that the drawings and detailed description theretoare not intended to limit the disclosure to the particular formdisclosed, but on the contrary, the intention is to cover allmodifications, equivalents and alternatives falling within the spiritand scope of the present disclosure as defined by the appended claims.

DETAILED DESCRIPTION Terms

The following is a glossary of terms used in the present application:

This specification includes references to “one embodiment” or “anembodiment.”

The appearances of the phrases “in one embodiment” or “in an embodiment”do not necessarily refer to the same embodiment. Particular features,structures, or characteristics may be combined in any suitable mannerconsistent with this disclosure.

Memory Medium—any of various types of memory devices or storage devices.The term “memory medium” is intended to include an installation medium,e.g., a CD-ROM, floppy disks 104, or tape device; a computer systemmemory or random access memory such as DRAM, DDR RAM, SRAM, EDO RAM,Rambus RAM, EEPROM, etc.; a non-volatile memory such as a Flash,magnetic media, e.g., a hard drive, or optical storage; registers, orother similar types of memory elements, etc. The memory medium maycomprise other types of memory as well or combinations thereof. Inaddition, the memory medium may be located in a first computer in whichthe programs are executed, or may be located in a second differentcomputer which connects to the first computer over a network, such asthe Internet. In the latter instance, the second computer may provideprogram instructions to the first computer for execution. The term“memory medium” may include two or more memory mediums which may residein different locations, e.g., in different computers that are connectedover a network.

Carrier Medium—a memory medium as described above, as well as a physicaltransmission medium, such as a bus, network, and/or other physicaltransmission medium that conveys signals such as electrical,electromagnetic, or digital signals.

Computer System—any of various types of computing or processing systems,including a personal computer system (PC), mainframe computer system,workstation, network appliance, Internet appliance, personal digitalassistant (PDA), smart phone, television system, grid computing system,or other device or combinations of devices. In general, the term“computer system” can be broadly defined to encompass any device (orcombination of devices) having at least one processor that executesinstructions from a memory medium.

Graphical Processing Unit—refers to a component that may reside on apersonal computer, workstation, or equivalent, and outputs video levelsfor each color or channel of a supported color model, e.g., for each ofthree colors, typically Red (R), Green (G), and Blue (B), for each pixelon the display. Each of these numbers is typically an 8 bit number, witha range of 0 to 255, although other ranges are possible.

Functional Unit (or Processing Element)—refers to various elements orcombinations of elements configured to process instructions and/or data.Processing elements include, for example, circuits such as an ASIC(Application Specific Integrated Circuit), portions or circuits ofindividual processor cores, entire processor cores, individualprocessors, programmable hardware devices such as a field programmablegate array (FPGA), and/or larger portions of systems that includemultiple processors, as well as any combinations thereof.

Projection—refers to the rendering of a 3D object, or content, using adisplay device such as a 3D stereoscopic system display on a twodimensional (2D) display. Thus, a projection may be described as themathematical function applied to objects within a virtual 3D scene todetermine the virtual position of the objects within a 3D space that maybe defined by the size of the and the point of view or perspective of auser.

Viewpoint—This term has the full extent of its ordinary meaning in thefield of computer graphics/cameras and specifies a location and/ororientation. For example, the term “viewpoint” may refer to a singlepoint of view (e.g., for a single eye) or a pair of points of view(e.g., for a pair of eyes). Thus, viewpoint may refer to the view from asingle eye, or may refer to the two points of view from a pair of eyes.A “single viewpoint” may specify that the viewpoint refers to only asingle point of view and a “paired viewpoint” or “stereoscopicviewpoint” may specify that the viewpoint refers to two points of view(and not one). Where the viewpoint is that of a user, this viewpoint maybe referred to as an eyepoint (see below) or “physical viewpoint”. Theterm “virtual viewpoint” refers to a viewpoint from within a virtualrepresentation or 3D scene. A viewpoint is synonymous with “point ofview” (POV). (See definition of POV below.)

Eyepoint—the physical location (and/or orientation) of a single eye or apair of eyes. A viewpoint above may correspond to the eyepoint of aperson. For example, a person's eyepoint has a corresponding viewpoint.

Point of View (POV)—a position and orientation. For example, a POV maybe a viewpoint or eyepoint, generally of a user, but may also be aviewpoint of an optical device, such as a camera. The POV is generally ameans to capture a relationship between two or more 6 degree of freedomobjects. In a typical application of the present techniques, a user'spair of eyes or head (view) are positioned in any X, Y, Z positionand/or pitch, yaw, roll orientation to a display device, e.g., a monitorscreen, which may have its own position in any X, Y, Z position and/orpitch, yaw, roll orientation. In this example, the POV can be defined asthe position/orientation of the user's view with respect to thepositioning/orientation of the display device. The POV determination maybe identified by a capture system. In a typical application of thepresent techniques, one or more tracking devices are attached to thedisplay device, such that the controller knows what the tracking systemtracks in the context of the display device, meaning the trackingsystem, being attached to the display device, is programmatically awareof the position/orientation of the display device, as well as anypotential change to the position/orientation of the display device.

The tracking device (which is identifying and tracking the user's view)identifies the position/orientation of the user's view, and thisinformation is then correlated to the tracking system's identificationof the viewing device's position/orientation (again, with respect to thedisplay device).

Frustum—refers to the region of virtual space that may be rendered by astereoscopic 3D display system. May be also referred to as the viewingfrustum or view frustum. Although the shape of the region may vary basedon the type of camera lens simulated, a frustum is generally the shapeof a rectangular pyramid. The planes that cut the frustum perpendicularto the viewing direction may be referred to as the near plane and thefar plane.

Coupled Zone—refers to a physical volume in which the user of a 3Dstereoscopic system may view 3D content within the human eye's naturaldepth of field. Put another way, the “coupled zone” of a 3D stereoscopicdisplay may refer to volume defined by a user's viewing angle, the sizeof the 3D stereoscopic display, and the distances in front of and behindthe 3D display in which a user may view objects for an extended periodof time without developing eye strain. Thus, the coupled zone of aparticular 3D stereoscopic display may also be referred to as the“comfort zone” of the particular 3D stereoscopic display, i.e., thephysical volume in which a user may view virtual images for an extendedperiod of time without experiencing eye strain, and thus, discomfort.

Note that in the physical world, when a person sees an object, theperson's eyes converge on, or look (individually aim) at, the object.Additionally, as the two eyes converge on the object, each eye's lensalso focuses (monoscopically) on the object. In this sense, both eyesfocus and converge on the object, thus focus and convergence are“coupled.”

In contrast, when looking at a display of 3D stereoscopic system, focusmust always remain on the display, whereas the eyes must converge atvarious depths in order to visualize, or see, the 3D illusion. Thus,focus and convergence appear to “de-couple.” Note that when focus andconvergence de-couple, eye strain may develop if focus and convergenceremain de-coupled for a period of time which may lead to discomfort forthe viewer.

Vertical Perspective—a perspective which is rendered for a viewpointwhich is substantially perpendicular to the display surface.“Substantially perpendicular” may refer to 90 degrees or variationsthereof, such as 89 and 91 degrees, 85-95 degrees, or any variationwhich does not cause noticeable distortion of the rendered scene. Avertical perspective may be a central perspective, e.g., having a single(and central) vanishing point. As used herein, a vertical perspectivemay apply to a single image or a stereoscopic image. When used withrespect to a stereoscopic image (e.g., presenting a stereoscopic imageaccording to a vertical perspective), each image of the stereoscopicimage may be presented according to the vertical perspective, but withdiffering single viewpoints.

Horizontal or Oblique Perspective—a perspective which is rendered from aviewpoint which is not perpendicular to the display surface For example,the term “horizontal perspective” may refer to a perspective which isrendered using a substantially 45 degree angled render plane inreference to the corresponding viewpoint. The rendering may be intendedfor a display which may be positioned horizontally (e.g., parallel to atable surface or floor) in reference to a standing viewpoint.“Substantially 45 degrees” may refer to 45 degrees or variationsthereof, such as 44 and 46 degrees, 40-50 degrees. Similarly, an obliqueperspective may refer to any angle that in not vertical or horizontal.As used herein, a horizontal perspective may apply to a single image ora stereoscopic image. When used with respect to a stereoscopic image(e.g., presenting a stereoscopic image according to a horizontalperspective), each image of the stereoscopic image may be presentedaccording to the distinct horizontal perspective, but with differingsingle viewpoints.

Another conception of the horizontal perspective as commonly used inthis invention is the projection of the intended rendered graphics tothe viewing device. With the POV determined, a horizontal or obliqueperspective engine may identify the correct graphics frustum in the 3Dspace, taking into account the position and orientation of the viewingdevice as defining position and orientation of the render plane of thefrustum and the user's view in position and orientation to define camerapoint of the frustum in relation to the render plane. The resultantprojection is then rendered onto the viewing device to be seen by theuser.

Position—the location or coordinates of an object (either virtual orreal). For example, position may include x, y, and z coordinates withina defined space. The position may be relative or absolute, as desired.Position may also include yaw, pitch, and roll information, e.g., whendefining the orientation of a viewpoint.

Stylus—peripheral devices or user control elements such as a handhelddevice, handheld pen device, handheld pointing device, hand, finger,glove, or any object used to directly interact with rendered virtualobjects as in a stereo rendered virtual projected objects.

World Scale—refers to a multiplier used to scale the entire 3D scenebeing rendered. In general, either the scene objects are scaled within agiven frustum or the frustum is scaled with a constant set of sceneobjects.

Stereo Level—refers to a percentage multiplier of the stereo effect. Forexample, a 0.50 stereo level would reduce the parallax—both positive andnegative—by half.

Field of View—refers to the angle between two rays each starting at theviewer's head position, and passing through the left and right edges ofthe screen.

Zero Parallax Plane (Position)—refers to the virtual plane associatedwith the surface of the display screen of a 3D display systemindependent of the head position or viewpoint of the user relative tothe display screen

Zero Parallax Offset—refers to a constant offset to the 3D scene renderto move the zero-parallax plane position in the scene.

Head-tracking Scale—refers to a scaling factor used as a multiplier ofthe user's actual head movements. May be used to create the impressionof greater or lesser movement.

Inter-pupillary Distance—refers to the distance between the left eye andright eye cameras in a 3D rendering system.

Approximately—refers to a value that is almost correct or exact withinsome specified tolerance. For example, approximately may refer to avalue that is within 1 to 10 percent of the exact (or desired) value. Itshould be noted, however, that the actual threshold value (or tolerance)may be application dependent. For example, in one embodiment,“approximately” may mean within 0.1% of some specified or desired value,while in various other embodiments, the threshold may be, for example,2%, 3%, 5%, and so forth, as desired or as required by the particularapplication.

Concurrent—refers to parallel execution or performance, where tasks,processes, or programs are performed in an at least partiallyoverlapping manner. For example, concurrency may be implemented using“strong” or strict parallelism, where tasks are performed (at leastpartially) in parallel on respective computational elements, or using“weak parallelism”, where the tasks are performed in an interleavedmanner, e.g., by time multiplexing of execution threads.

Automatically—refers to an action or operation performed by a computersystem (e.g., software executed by the computer system) or device (e.g.,circuitry, programmable hardware elements, ASICs, etc.), without userinput directly specifying or performing the action or operation. Thusthe term “automatically” is in contrast to an operation being manuallyperformed or specified by the user, where the user provides input todirectly perform the operation. An automatic procedure may be initiatedby input provided by the user, but the subsequent actions that areperformed “automatically” are not specified by the user, i.e., are notperformed “manually”, where the user specifies each action to perform.For example, a user filling out an electronic form by selecting eachfield and providing input specifying information (e.g., by typinginformation, selecting check boxes, radio selections, etc.) is fillingout the form manually, even though the computer system must update theform in response to the user actions. The form may be automaticallyfilled out by the computer system where the computer system (e.g.,software executing on the computer system) analyzes the fields of theform and fills in the form without any user input specifying the answersto the fields. As indicated above, the user may invoke the automaticfilling of the form, but is not involved in the actual filling of theform (e.g., the user is not manually specifying answers to fields butrather they are being automatically completed). The presentspecification provides various examples of operations beingautomatically performed in response to actions the user has taken.

Comprising—this term is open-ended. As used in the appended claims, thisterm does not foreclose additional structure or steps. Consider a claimthat recites: “A system comprising a display . . . . ” Such a claim doesnot foreclose the apparatus from including additional components (e.g.,a voltage source, a light source, etc.).

Configured To—various units, circuits, or other components may bedescribed or claimed as “configured to” perform a task or tasks. In suchcontexts, “configured to” is used to connote structure by indicatingthat the units/circuits/components include structure (e.g., circuitry)that performs those task or tasks during operation. As such, theunit/circuit/component can be said to be configured to perform the taskeven when the specified unit/circuit/component is not currentlyoperational (e.g., is not on). The units/circuits/components used withthe “configured to” language include hardware—for example, circuits,memory storing program instructions executable to implement theoperation, etc. Reciting that a unit/circuit/component is “configuredto” perform one or more tasks is expressly intended not to invoke 35U.S.C. §112, sixth paragraph, for that unit/circuit/component.Additionally, “configured to” can include generic structure (e.g.,generic circuitry) that is manipulated by software and/or firmware(e.g., an FPGA or a general-purpose processor executing software) tooperate in manner that is capable of performing the task(s) at issue.

First, Second, etc.—these terms are used as labels for nouns that theyprecede, and do not imply any type of ordering (e.g., spatial, temporal,logical, etc.). For example, in a system having multiple trackingsensors (e.g., cameras), the terms “first” and “second” sensors may beused to refer to any two sensors. In other words, the “first” and“second” sensors are not limited to logical sensors 0 and 1.

Based On—this term is used to describe one or more factors that affect adetermination. This term does not foreclose additional factors that mayaffect a determination. That is, a determination may be solely based onthose factors or based, at least in part, on those factors. Consider thephrase “determine A based on B.” While B may be a factor that affectsthe determination of A, such a phrase does not foreclose thedetermination of A from also being based on C. In other instances, A maybe determined based solely on B.

FIG. 4—Exemplary System

FIG. 4 illustrates an exemplary system that may be configured to performvarious embodiments described below.

In the embodiment of FIG. 4, computer system 100 may include chassis110, display 150A and display 150B (which may collectively be referredto as display 150 or “at least one display” 150), keyboard 120, mouse125, user control element 130, eyewear 140, at least two cameras 160,and stylus caddy 170. Note that in some embodiments, two displays 150Aand 150B may not be used; instead, a single display 150 may be used insuch embodiments. In various embodiments, at least one of the displays150A and 150B may be a stereoscopic display. For example, in oneembodiment, both of the displays 150A and 150B may be stereoscopicdisplays. Or, in other embodiments, the single display 150 may be astereoscopic display. It is noted that a stereoscopic display may alsobe configured to display two-dimensional (2D) objects and may beconfigured to operate in a 2D mode.

The chassis 110 may include various computer components such asprocessors, at least one memory medium (e.g., RAM, ROM, hard drives,etc.), graphics circuitry, audio circuitry, and other circuitry forperforming computer tasks, such as those described herein. The at leastone memory medium may store one or more computer programs or softwarecomponents according to various embodiments of the present invention.For example, the memory medium may store one or more graphics engineswhich are executable to perform some of the techniques described herein.In certain embodiments the graphics engine may be implemented on or by afunctional unit or processing element. As used herein, and as noted inthe Terms section above, the term functional unit or processing elementrefers to various elements or combinations of elements configured toprocess instructions and/or data. Processing elements include, forexample, circuits such as an ASIC (Application Specific IntegratedCircuit), portions or circuits of individual processor cores, entireprocessor cores, individual processors, programmable hardware devicessuch as a field programmable gate array (FPGA), and/or larger portionsof systems that include multiple processors, as well as any combinationsthereof.

The memory medium may also store data (and/or program instructions)(e.g., implementing or specifying a computer model) representing avirtual space, which may be used for projecting a 3D scene, such asscene 180, of the virtual space via the display(s) 150. Further, one ormore memory mediums may store software which are executable to performthree-dimensional spatial tracking (e.g., user view tracking, usercontrol tracking, etc.), content processing, or other features, asdescribed herein. Additionally, the memory medium may store operatingsystem software, as well as other software for operation of the computersystem. Various embodiments further include receiving or storinginstructions and/or data implemented in accordance with the foregoingdescription upon a carrier medium.

As indicated above, the computer system 100 may be configured to displaya three dimensional (3D) scene (e.g., via stereoscopic paired images),or 3D content, such as scene 180, using the display 150A and/or thedisplay 150B. The computer system 100 may also be configured to displaya “view” of the 3D scene using the display 150A, the display 150B,and/or another display, either fixed in position and orientation ormovable in position and orientation, as described in more detail below.The “view” of the 3D scene, or content, may refer to a displayed portionof the 3D scene from a viewpoint within the 3D scene. A viewpoint withinthe 3D scene may be referred to as a “virtual viewpoint”. The view maybe stereoscopic, e.g., may be displayed on a stereoscopic display.Alternatively, the view may be monoscopic (not stereoscopic), and may bedisplayed on either a monoscopic display or a stereoscopic display. Notethat a monoscopic image or scene displayed on a stereoscopic display mayappear the same as on a monoscopic display system.

It should be noted that the embodiment of FIG. 4 is exemplary only, andother numbers of displays are also envisioned. For example, the computersystem 100 may include only a single display or more than two displays,the displays may be arranged in different manners than shown, or thedisplays may be portable. In this particular embodiment, the display150A is configured as a vertical display (which is perpendicular to auser's line of sight) and the display 150B is configured as a horizontaldisplay (which is parallel or oblique to a user's line of sight). Thevertical display 150A may be used (e.g., via instructions sent by agraphics engine executing in the chassis 110) to provide images whichare presented according to a vertical (or central) perspective and thedisplay 150B may be used (e.g., via instructions sent by a graphicsengine executing in the chassis 110) to provide images which arepresented according to a horizontal perspective. Descriptions ofhorizontal and vertical perspectives are provided herein. Additionally,while the displays 150 are shown as flat panel displays, in otherembodiments, they may be any type of system which is capable ofdisplaying images, e.g., projection systems. For example, display(s) 150may be or include, for example, a CRT (cathode ray tube) monitor, a LCD(liquid crystal display) monitor, or a front projection or a backprojection screen or surface with a plurality of projectors, amongothers. Display(s) 150 may include a light emitting diode (LED)backlight or other type of backlight.

Either or both of the displays 150A and 150B may present (display)stereoscopic images for viewing by the user. By presenting stereoscopicimages, the display(s) 150 may present a 3D scene conveying depth forthe user. This conveyed depth 3D (i.e., 3D) scene may be considered orreferred to as an illusion or simulated 3D since the actual providedimages are 2D, but the scene is conveyed in 3D via the user'sinterpretation of the provided images. In order to properly view thestereoscopic images (one for each eye for each image frame), the usermay wear eyewear 140. Eyewear 140 may be any of anaglyph glasses,polarized glasses, shutter glasses, lenticular glasses, etc., amongothers. In embodiments using anaglyph glasses, images for a first eyeare presented according to a first color (and the corresponding lens hasa corresponding color filter) and images for a second eye are projectedaccording to a second color (and the corresponding lens has acorresponding color filter). With polarized glasses, images arepresented for each eye using orthogonal polarizations, and each lens ofthe eyewear has the corresponding orthogonal polarization for receivingthe corresponding image. With shutter glasses, each lens is synchronizedwith respect to left and right eye images provided by the display(s)150, e.g., in alternating fashion. The display may provide bothpolarizations simultaneously or in an alternating manner (e.g.,sequentially), as desired. Thus, the left eye may be allowed to only seeleft eye images during the left eye image display time and the right eyemay be allowed to only see right eye images during the right eye imagedisplay time. With lenticular glasses, images form on cylindrical lenselements or a two dimensional array of lens elements. Note that in someembodiments, the display may be an autostereo display and may includelenticular lenses on the display itself, thereby negating the need forcomplementary glasses. The stereoscopic image may be provided viaoptical methods, where left and right eye images are provided only tothe corresponding eyes using optical means such as prisms, mirror(s),lens(es), and the like. Large convex or concave lenses can also be usedto receive two separately projected images to the user.

In one embodiment, eyewear 140 may be used as a position input device totrack the user view (e.g., eyepoint or point of view (POV)) of a userviewing a 3D scene presented by the system 100. For example, eyewear 140may provide information (e.g., position, orientation, etc.) that isusable to determine the position and orientation of the point of view ofthe user, e.g., via triangulation. In some embodiments, the positioninput device may use a light sensitive detection system, e.g., mayinclude an infrared detection system, to detect the position of theuser's head to allow the user freedom of head movement. Otherembodiments of the input device(s) may use the triangulation method ofdetecting the user point of view location, such as via one or moresensors (e.g., two cameras, such as CCD cameras) providing positionand/or orientation data suitable for the head or eye tracking. In aparticular embodiment, the one or more sensors may perform featurerecognition to recognize features on the user's head or face to providethe position and/or orientation data suitable for the head or eyetracking. The input device(s), such as a keyboard, mouse, trackball,joystick, or the like, or combinations thereof, may be manually operatedby the user to indicate the correct display of the horizontalperspective display images. However, any method for tracking theposition of the user's head or point of view may be used as desired.Accordingly, the 3D scene may be rendered from the perspective (or pointof view) of the user such that user may view the 3D scene with minimaldistortions (e.g., since it is based on the point of view of the user).Thus, the 3D scene may be particularly rendered for (and in accordancewith) the point of view of the user, using the position input device.

The relationships among the position/orientation of the display(s) 150and the point of view of the user may be used to map a portion of thevirtual space to the physical space of the system 100. In essence, thephysical space and components used may be mapped to the virtual model inorder to accurately render, in terms of perspective to projection, a 3Dscene of the virtual space.

One or more of the user input devices (e.g., the keyboard 120, the mouse125, the user control element 130, pointing device, user control device,etc.) may be used to interact with the presented 3D scene. For example,a user control element may be used to directly interact with the virtualobjects of the 3D scene (via the viewed projected objects). Thus, theuser control element 130 (shown as a stylus) or simply the user's handsmay be used to directly interact with virtual objects of the 3D scene.Such direct interaction may be possible with “open space” portions ofthe 3D scene, i.e., the area between the display and the user. Thus, atleast a portion of the 3D scene may be presented in this “open space”,which is in front of or otherwise outside of the at least one display.In some embodiments, at least a portion of the 3D scene may appear as ahologram above the surface of the display 150. For example, when thehorizontal display 150B is used, the 3D scene may be seen as hoveringabove the horizontal display. Note that when presenting the 3D scene onthe horizontal display, the position and orientation of the display tothe user's viewpoint may be correlated to the frustum's render planewhen rendering the 3D scene. Additionally, it should be noted, that aportion of the 3D scene may also be presented as appearing behind thedisplay surface, which is not in “open space”. Thus, “open space” refersto a space which the user is able to freely move in and interact with(e.g., where the user is able to place his hands in the space), asopposed to a space the user cannot freely move in and interact with(e.g., where the user is not able to place his hands in the space, suchas below the display surface). However, in the case where the user maynot place his hands in the space, the user may use a scene generatingvirtual extension that appears to the user to be able to virtuallymanipulate virtual objects not appearing the “open space”. Thus, “openspace” may be considered to be a “hands-on volume” as opposed to an“inner-volume”, which may be under the surface of the display(s). Thus,the user may interact with virtual objects in the open space becausethey appear as being proximate to the user's own physical space. Saidanother way, the inner volume is located behind (or under) the viewingsurface, and so presented objects appear to be inside the physicalviewing device. Thus, objects of the 3D scene presented within the innervolume do not share the same physical space with the user and theobjects therefore cannot be directly and physically manipulated by handsor hand-held tools such as user control element 130 shown as a stylus.Rather, they may be manipulated indirectly, e.g., via a computer mouse,a joystick, or virtual representations of hands, handheld tools, or astylus.

In some embodiments, system 100 may include one or more sensors 160. Theone or more sensors 160 may be included in a point of view (POV)tracking system. In certain embodiments, the one or more sensors 160 maybe affixed to one or more reference points attributable to or withrespect to, the display and may provide a correlation of position andorientation of what is tracked to the position and orientation of thedisplay. FIG. 4 illustrates an embodiment using four cameras 160. Forinstance, two of the four cameras 160 may be used to sense a user view(e.g., point of view) and the other two cameras 160 may be used to sensea user control element (e.g., pointing device, stylus, hand, glove, oneor more fingers, etc.). Sensors 160 may be used to image a user ofsystem 100, track a user's movement, or track a user's head or eyes,among other contemplated functions. In one embodiment, cameras 160 maytrack a position and/or an orientation of user control element 130. Theinformation regarding the position and/or orientation of the usercontrol element 130 provided by the one or more sensors 160 may be usedin conjunction with other positional information of the system (e.g., anaccelerometer and/or gyroscope within the stylus itself) to perform moreprecise 3D tracking of the user control element 130. The one or moresensors 160 may be spatially separated from one another and placed in aposition to view a volume that encompasses the view frustum, i.e., wherea user will view stereo imagery. Sensors 160 may also be far enoughapart from each other to provide for a separation of view for a truethree-axis triangulation determination. System 100 may also include acaddy 170 to store user control element 130. Caddy 170 may also be usedto calibrate the orientation of the stylus to a known roll, pitch, andyaw, and so may be in a fixed position relative to cameras 160.

In one embodiment, the system 100 may be configured to couple to anetwork, such as a wide area network, via an input. The input may beconfigured to receive image data over the network from a system similarto system 100. In other embodiments, a POV tracking system may includecameras 160. Cameras 160 may be configured to provide visual informationregarding a user such that a POV, e.g., the position and orientation, ofthe user may be determined. However, it should be noted that any type ofvarious POV tracking techniques or devices may be used as desired. Notethat as used herein, point of view (POV) of a user refers to theperspective or POV from which a user optically views an object or image,i.e., a user's visual POV, and thus is defined with respect to thedisplay device of the system. In some embodiments, the POV may be a 6degree of freedom (6DOF) POV, e.g., three position coordinates and threeorientation coordinates, although any POV may be used as desired, e.g.,three position coordinates and two or three orientation coordinates, andso forth.

Note that in some embodiments, the POV tracking system may rely at leastin part on the components of chassis 110 to determine the POV, e.g., viaexecution of one more programs on a processor or functional unit ofchassis 110, although in other embodiments the POV tracking system mayoperate independently, e.g., may have its own processor or functionalunit.

In certain embodiments, the system may include components implementing aperspective based image capture system, for capturing images of targetobject at a location remote from the system. For example, theperspective based image capture system may include an input configuredto couple to a network for receiving information regarding a point ofview (POV) from a POV tracking system at a remote location. Theinformation regarding the POV may indicate a position and/or orientationof a remote user. The perspective based image capture system may furtherinclude another image capture system for capturing images of a targetobject. More specifically, the image capture system may be configured tocapture one or more images from a first perspective based on theinformation regarding the POV received by the input.

The user may be able to specify or otherwise manipulate a virtualviewpoint within the 3D scene presented by the display(s) 150. A view ofthe 3D scene may be presented based on the virtual viewpoint, either byone or more of the display(s) 150 or another display, as desired. Thisview of the 3D scene may be stereoscopic or monoscopic, as desired. Notethat in some embodiments, the virtual viewpoint may change as a user'seyepoint(s) changes. Additionally, the user's eyepoint(s) may be trackedby a tracking system as described above.

A 3D scene generator (e.g., content processing system) stored andexecuted in the chassis 110 may be configured to dynamically change thedisplayed images provided by the display(s) 150. More particularly, the3D scene generator may update the displayed 3D scene based on changes inthe user view, user control (e.g., manipulations via the user inputdevices), etc. Such changes may be performed dynamically at run-time,and may be performed in real-time. The 3D scene generator may also keeptrack of peripheral devices (e.g., eyewear 140) and/or user controlelements (e.g., user control element 130) to ensure synchronizationbetween the peripheral devices and/or the user control elements, thefrustum, the frustum render plan, the rendering, and the correspondingdisplayed images. The system may further include a calibration unit toensure proper mapping of the peripheral device to the display images andproper mapping between the projected rendered images and the virtualimages stored in the memory of the chassis 110.

Thus, the system 100 may present a 3D scene which the user may virtuallyinteract with in real time. The system may comprise real-time electronicdisplay(s) 150 that may present or convey projected images in the openspace based on the perspective of the user, and a peripheral device oruser control element 130 that may allow the user to interact with the 3Dscene with hand controlled or hand-held tools. The system 100 may alsoinclude means to manipulate the displayed image such as magnification,zoom, rotation, movement, and even display a new image. However, asnoted above, in some embodiments, the system may facilitate suchmanipulations via the user's hands, e.g., without hand-held tools.

Further, while the system 100 is shown as including horizontal display150B since it simulates the user's visual experience with the horizontalground, other viewing surfaces may offer a similar 3D illusionexperience. For example, the 3D scene may appear to be hanging from aceiling by projecting the horizontal perspective images onto a ceilingsurface, or may appear to be floating from a wall by projectinghorizontal perspective images onto a vertical wall surface, or may be auser handheld device, where the scene may either appear to be moving inspace with the movement of the portable device or the portable devicemay appear to be moved away, thereby passing by the scene. Moregenerally, any other variations in display orientation and perspective(or any other configuration of the system 100) may be used as desired.

Thus, in certain embodiments, the system may include instructions storedon a memory medium of the system and executable by a processor orfunctional unit of the system to perform navigation of a 3D scene viatracked user head position. As discussed above, the 3D stereoscopicsystem may include components or systems which may allow the point ofview (POV) of the user to be tracked. Accordingly, in one embodiment,software or a software module may include a user head trackingnavigation mode. The head tracking navigation mode may be enabled by avariety of triggers. For example, the head tracking navigation mode maybe enabled at startup of the 3D stereoscopic system or through some formof user interaction that may trigger startup of the head trackingnavigation mode. The trigger may be based on the selection of the headtracking navigation mode via a user interface displayed within a 3Dscene, such as a menu. Additionally, the trigger may be external to the3D scene. Thus, the trigger may be an input device such as a switch orbutton of a user control element. The user control element may be a userinput device, such as a stylus. Note that the system may include morethan one trigger for enabling the head tracking navigation mode.

Once the head tracking navigational mode has been enabled, a referencepoint of view (POV) may be established via a head tracking, or POVtracking, system as described above. The reference POV may include areference user head position and a reference user head orientation.Thus, via the POV tracking system of the 3D stereoscopic system, userhead POV may be tracked relative to the reference POV. In other words,tracking the user's head POV may monitor user head positionaldisplacements and user head angular rotations relative to the referencePOV.

Further, in response to tracking the user's head POV, the system may beconfigured to adjust a camera POV used to render the 3D stereoscopicscene. The adjustment may be based on a non-linear mapping betweenchanges in the camera POV and the user head positional displacements anduser head angular rotations relative to the reference POV. In otherwords, the non-linear mapping may be based on changes in user headposition and orientation relative to a reference position andorientation of the user's head.

The non-linear mapping may include a mapping of user head positionaldisplacements relative to the reference POV to translational movementsin the camera view. Further, the non-linear mapping may include amapping of user head angular rotations relative to the reference POV torotations in the camera POV.

In one embodiment the non-linear mapping may be used to adjust one ormore of various 3D stereoscopic rendering variables, including forexample, but not limited to, scaling, such as the world scale, stereolevel, field of view, and/or parallax offset, among others. In someembodiments, the adjustments to the one or more stereo variables may beoptimized to maintain optimum viewer comfort. Note that in certainembodiments, the adjustments may be dynamic and may occur in real-time.In other words, based on the head position driven navigation of thescene, dynamic adjustments to the one or more stereo variables may bemade. Accordingly, by adjusting, or changing, the stereo settings inresponse to the head position and the head-driven navigation, the scenemay be maintained with an optimal viewing comfort. Further, visualartifacting at the near clip plane may be minimized or removed.

Hence, in some embodiments stereo settings are programmatically chosento best represent the virtual appearance given the navigating activityand the breadth of the scene to be rendered.

FIGS. 5A-5C illustrate changes to a frustum based on changes in user POVaccording to embodiments. As illustrated in FIG. 5A, a first frustum 606may correspond to a first POV 600 of user 602 as user 602 interacts withdisplay 604 of a 3D stereoscopic system. Note that the 3D stereoscopicsystem may be similar to or the same as the 3D stereoscopic systemdescribed above in reference to FIG. 4. Thus, for example, 3Dstereoscopic system 604 may render a 3D scene on display 604 that may beviewable by user 602 at POV 600. As illustrated in FIG. 5B, as user 602moves away from display 604, user 602 may have a second POV 610 and acorresponding second frustum 616. Similarly, as illustrated in FIG. 5C,user 602 may move even further away from display 604 resulting in athird POV 620 and a corresponding third frustum 626. Thus, according tosome embodiments, and as discussed below with reference to FIG. 6, asthe user moves further away from the display, and the user'scorresponding frustum changes, a world scale may be dynamicallyadjusted, effectively allowing the user to zoom out by changing headposition.

FIG. 6 illustrates an example of an embodiment of the non-linear mappingwith respect to frustum field of view angle as the world scale of the 3Dscene is adjusted. As shown, compared to the prior art, as a user movesthe user POV further away from the display screen, as illustrated inFIGS. 5A-5C, the frustum field of view angle may be increased, and theworld scale may be dynamically adjusted, effectively allowing the userto zoom out. In other words, the movement of the user's head away fromzero parallax plane of the scene may cause the system to adjust therendering camera POV to allow for rapidly achieving an overall“birds-eye” view of the 3D scene. Thus, by changing the world scale,navigation can automatically move larger distances as the user pullsback whereas in the prior art, the world scale remains constant as thefrustum field of view angle is increased.

For example, as a user moves the user POV away from the screen (furtherback from the screen as illustrated in FIGS. 5B and 5C), the camera POVmay be moved farther from the scene. Thus, for example, if the scenewere a baseball stadium, the user could alter the camera POV from beingpositioned in the front row, to, as the user POV moves further from thedisplay, the camera POV being positioned in the top row of the stadium.Note that as the camera POV is positioned further from the action (e.g.,baseball field), the effect of head motion, such as moving the head leftor right, on the perceived image may be lessened. Thus, in certainembodiments this may be compensated for by adjusting the world scale tomake the virtual world appear smaller, resulting in the user headmovement still having a visual affect.

Although the embodiment depicted in FIG. 6 illustrates the non-linearmapping of world scale to frustum field of view angle (camera POV),non-linear mapping of other 3D stereoscopic rendering variables tofrustum field of view angle may aid in head tracked navigation. Forexample, stereo level, which may affect the zone of comfort (coupledzone) between the user and the display, may be dynamically lowered whenthe user navigates to a position that has a deeper perceived depth offield. Additionally, in certain embodiments, the field of view may benon-linearly adjusted, via the rendering camera POV, to create a“telescopic lens” or “scope” effect as the user focuses in on an objectin the scene. Additionally, the stereo level may be dynamically changed,i.e., in real-time, to ensure that the 3D scene presented to the userremains within the coupled zone.

Further, in some embodiments, the zero parallax offset, which may affectthe perceived depth of objects from the rendering screen, may bedynamically adjusted to maintain the feeling that the screen is a“window”, by re-positioning the zero parallax plane to place the sceneat an optimal viewing depth. Note that in some embodiments, theadjustment of the zero parallax plane may be non-linearly mapped to thefrustum field of view angle.

In certain embodiments, there may be a non-linear relationship betweenthe near plane, or near-clip plane, of the frustum field of view anduser head POV. In such embodiments, the near-clip plane may bedynamically adjusted, e.g., in real-time, to fall at a constant planewithin the scene in contrast to the prior art constant distance from thecamera. This may allow minor changes in user head position to not changethe visually perceived clip plane. In certain embodiments, the near-clipplane may be dynamically adjusted via adjustment to a head-trackingscale.

In further embodiments, the rate of the change of the camera POV may benon-linearly mapped to changes in user head POV, i.e., changes in userhead position and orientation. For example, if the user POV is movedcloser to display as if to look closer to the objects within the 3Dscene, the corresponding projection of the scene may correlate to afraction of the rate of change of the head position.

FIG. 7: Block Diagram of a Method for Non-Linear Navigation of a 3DScene

FIG. 7 illustrates an exemplary embodiment of a method for navigating athree dimensional (3D) stereoscopic scene displayed via a 3Dstereoscopic display system. The method shown in FIG. 7 may be used inconjunction with any of the computer systems, devices, or software shownin, or described in reference to, the above Figures, among othersystems, devices, and software. In various embodiments, some of themethod elements shown may be performed concurrently, in a differentorder than shown, or may be omitted. Additional method elements may alsobe performed as desired. As shown, this method may operate as follows.

In 702, a user head tracking navigational mode of a 3D stereoscopicdisplay system may be enabled. The 3D stereoscopic display system may besimilar to, or include features and components similar to, the 3Dstereoscopic display systems described above in reference to FIGS. 4-6.In certain embodiments, the user head tracking navigational mode may beenabled via user input to the 3D stereoscopic display system. In oneembodiment, the user input may be received via a user control element,such as a stylus. In another embodiment, the user input may be receivedvia a user interface displayed within the 3D stereoscopic scene. Ofcourse, in other embodiments, any type of user input means may be usedas desired.

In 704, a reference point of view (POV) may be established. Note that aPOV generally refers to a position and an orientation, and thus thereference POV may include a reference position and a referenceorientation. For example, a POV may be a viewpoint or eyepoint,generally of a user, but may also be a viewpoint of an optical device,such as a camera, or the viewpoint of a virtual device, such as avirtual camera. Additionally, a POV may define a frustum view angle, orfrustum viewing angle. The POV is generally a means to capture or encodea relationship between two or more 6 (or possibly fewer) degree offreedom objects. In a typical application of the present techniques, auser's pair of eyes or head (view) are positioned in any X, Y, Zposition and/or pitch, yaw, roll orientation with respect to a displaydevice, e.g., a monitor screen, which may have its own X, Y, Z positionand/or pitch, yaw, roll orientation.

In 706, a POV of the user's head may be tracked. In some embodiments,the tracking may be via a user head tracking system as described abovein reference to FIG. 4. The tracking may monitor both positionaldisplacements of the user's head and angular rotations of the user'shead relative to the reference POV established in step 704.

In 708, a camera POV used to render the 3D stereoscopic scene may beadjusted. Note that the camera POV may correspond, or correlate to, afrustum, or frustum field of view angle, used to render the 3Dstereoscopic scene. In one embodiment, the adjustment of the camera POVmay be based on a non-linear mapping between changes, or rates ofchange, of the camera POV and displacements, or rates of displacement,of user head position and rotations, or rates of rotation, of user headangle (i.e., orientation), with respect to, or relative to, thereference POV. In other words, the camera POV used to render the 3Dstereoscopic scene may be adjusted non-linearly with respect tomovements, or rates of movements, of the user's head with respect to areference POV. Thus, in certain embodiments, the non-linear mapping mayinclude a mapping of user head positional displacements relative to thereference POV to translational movements in the camera POV and a mappingof user head angular rotations relative to the reference POV torotations in the camera POV. Further, in some embodiments, the mappingmay also include a mapping of rate of change of user head positionaldisplacements relative to the reference POV to rate of change oftranslational movements in the camera POV and a mapping of rate ofchange of user head angular rotations relative to the reference POV torate of change of rotations in the camera POV.

In one particular embodiment, adjusting the camera POV may also includeadjusting one or more 3D stereoscopic rendering variables. In suchembodiments, the adjustment may also be based on a non-linear mapping ofeach of the one or more 3D stereoscopic rendering variables to thecamera POV, where the 3D stereoscopic rendering variables may include aworld scale variable, a stereo level variable, a zero parallax offsetvariable, and/or a head-tracking scale variable, among others.

Note that in some embodiments, the mapping may be performed via acorrelated table of mapped variables. In other embodiments, the mappingmay be performed via a continuous function. In certain embodiments, themapping may be performed via a discontinuous function.

It should be noted that the above-described embodiments are exemplaryonly, and are not intended to limit the invention to any particularform, function, or appearance. Moreover, in further embodiments, any ofthe above features may be used in any combinations desired. In otherwords, any features disclosed above with respect to one method or systemmay be incorporated or implemented in embodiments of any of the othermethods or systems.

Although the embodiments above have been described in considerabledetail, numerous variations and modifications will become apparent tothose skilled in the art once the above disclosure is fully appreciated.It is intended that the following claims be interpreted to embrace allsuch variations and modifications.

We claim:
 1. A method for navigating a three dimensional (3D)stereoscopic scene displayed via a 3D stereoscopic display system, themethod comprising: enabling a user head tracking navigational mode ofthe 3D stereoscopic display system; establishing a reference point ofview (POV), wherein the reference POV comprises a reference user headposition and a reference user head orientation; tracking user head POV,wherein said tracking monitors user head positional displacements anduser head angular rotations relative to the reference POV; andadjusting, in response to said tracking, a camera POV used to render the3D stereoscopic scene, wherein said adjusting is based on a non-linearmapping between changes in the camera POV and the user head positionaldisplacements and user head angular rotations relative to the referencePOV, and wherein the non-linear mapping comprises: a mapping of userhead positional displacements relative to the reference POV totranslational movements in the camera POV; and a mapping of user headangular rotations relative to the reference POV to rotations in thecamera POV.
 2. The method of claim 1, wherein said enabling comprises:receiving user input enabling the head tracking navigational mode viaone or more of: a user interface displayed within the 3D stereoscopicscene; or an input device of the 3D stereoscopic display system.
 3. Themethod of claim 2, wherein the input device is a user control element.4. The method of claim 1, wherein said adjusting further comprisesadjusting one or more 3D stereoscopic rendering variables, and whereinsaid adjusting is further based on a non-linear mapping of each of theone or more 3D stereoscopic rendering variables to the camera POV. 5.The method of claim 4, wherein the one or more 3D stereoscopic renderingvariables comprise one or more of: a world scale variable; a stereolevel variable; a zero parallax offset variable; or a head-trackingscale variable.
 6. The method of claim 1, wherein the non-linear mappingfurther comprises: a mapping of rate of change of user head positionaldisplacements relative to the reference POV to rate of change oftranslational movements in the camera POV; and a mapping of rate ofchange of user head angular rotations relative to the reference POV torate of change of rotations in the camera POV.
 7. The method of claim 1,wherein said adjusting occurs in real-time.
 8. The method of claim 1,wherein the camera POV corresponds to a frustum field of view angle. 9.A non-transitory computer readable memory medium storing programminginstructions for navigating a three dimensional (3D) stereoscopic scenedisplayed via a 3D stereoscopic display system, wherein the programminginstructions are executable by a processor to: enable a user headtracking navigational mode of the 3D stereoscopic display system;establish a reference point of view (POV), wherein the reference POVcomprises a reference user head position and a reference user headorientation; track user head POV, wherein said tracking monitors userhead positional displacements and user head angular rotations relativeto the reference POV; and adjust, in response to tracking user head POV,a camera POV used to render the 3D stereoscopic scene, wherein saidadjusting is based on a non-linear mapping between changes in the cameraPOV and the user head positional displacements and user head angularrotations relative to the reference POV, and wherein the non-linearmapping comprises: a mapping of user head positional displacementsrelative to the reference POV to translational movements in the cameraPOV; and a mapping of user head angular rotations relative to thereference POV to rotations in the camera POV.
 10. The non-transitorycomputer readable memory medium of claim 9, wherein to enable a userhead tracking navigational mode of the 3D stereoscopic display systemthe programming instructions are further executable by a processor to:receive user input enabling the head tracking navigational mode via oneor more of: a user interface displayed within the 3D stereoscopic scene;or an input device of the 3D stereoscopic display system.
 11. Thenon-transitory computer readable memory medium of claim 10, wherein theinput device is a user control element.
 12. The non-transitory computerreadable memory medium of claim 9, wherein to adjust the camera POV theprogramming instructions are further executable by a processor to adjustone or more 3D stereoscopic rendering variables, and wherein saidadjusting is further based on a non-linear mapping of each of the one ormore 3D stereoscopic rendering variables to the camera POV.
 13. Thenon-transitory computer readable memory medium of claim 12, wherein theone or more 3D stereoscopic rendering variables comprise one or more of:a world scale variable; a stereo level variable; a zero parallax offsetvariable; or a head-tracking scale.
 14. The non-transitory computerreadable memory medium of claim 9, wherein the non-linear mappingfurther comprises: a mapping of rate of change of user head positionaldisplacements relative to the reference POV to rate of change oftranslational movements in the camera POV; and a mapping of rate ofchange of user head angular rotations relative to the reference POV torate of change of rotations in the camera POV.
 15. The non-transitorycomputer readable memory medium of claim 9, wherein said adjusting isexecuted in real-time.
 16. The non-transitory computer readable memorymedium of claim 9, wherein the camera POV corresponds to a frustum fieldof view angle.
 17. A system for navigating a three dimensional (3D)stereoscopic scene displayed via a 3D stereoscopic display system,comprising: a 3D stereoscopic display system, comprising: a displayscreen; a user head tracking system; and a functional unit coupled tothe user head tracking system and the display screen, wherein thefunctional unit is configured to: enable a user head trackingnavigational mode of the 3D stereoscopic display system, wherein theuser's head is tracked via the user head tracking system; establish areference point of view (POV), wherein the reference POV comprises areference user head position and a reference user head orientation;track user head POV via the user head tracking system, wherein saidtracking monitors user head positional displacements and user headangular rotations relative to the reference POV; and adjust, in responseto tracking user head POV, a camera POV used to render the 3Dstereoscopic scene via the display screen, wherein said adjusting isbased on a non-linear mapping between changes in the camera POV and theuser head positional displacements and user head angular rotationsrelative to the reference POV, and wherein the non-linear mappingcomprises: a mapping of user head positional displacements relative tothe reference POV to translational movements in the camera POV; and amapping of user head angular rotations relative to the reference POV torotations in the camera POV.
 18. The system of claim 17, furthercomprising: an input device; wherein to enable a user head trackingnavigational mode of the 3D stereoscopic display system the functionalunit is further configured to: receive user input enabling the headtracking navigational mode via one or more of: a user interfacedisplayed within the 3D stereoscopic scene; or the input device.
 19. Thesystem of claim 17, wherein to adjust the camera POV the functional unitis further configured to adjust one or more 3D stereoscopic renderingvariables, and wherein said adjusting is further based on a non-linearmapping of each of the one or more 3D stereoscopic rendering variablesto the camera POV.
 20. The system of claim 17, wherein the non-linearmapping further comprises: a mapping of rate of change of user headpositional displacements relative to the reference POV to rate of changeof translational movements in the camera POV; and a mapping of rate ofchange of user head angular rotations relative to the reference POV torate of change of rotations in the camera POV.